I recently presented some statistics and trends 2010 about LinkedIn, based on directly measured visitor stats. Another way of getting a better understanding of the demographics of the LinkedIn user is the LinkedIn Direct Ads section.
In the infographic below an overview is given of some interesting numbers about member participation per country, industry type, company size and job role in LinkedIn. Please note that Gender and Age stats are not accurate due to the fact that these are not mandatory fields on LinkedIn.com (most of the people don’t complete this info so this data is calculated).
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High Tech, Finance and Manufacturing are the top industries on LinkedIn. The Human Resources function only represents 4% of the total user population. If you are looking for Engineers you should definitely start using LinkedIn; 15% is working in Engineering. Sales profiles are, not surprisingly, also well represented on here.